CONSTRUCTION AND ANALYSIS OF AN miRNA-mRNA NETWORK TO IDENTIFY HUB REGULATORS IN DROUGHT-STRESSED COWPEA

Abstract

Drought stress severely threatens cowpea (Vigna unguiculata), a crop vital to food security in sub-Saharan Africa. While naturally resilient, the molecular mechanisms governing its drought response are poorly understood. This study aimed to map the post-transcriptional regulatory network of microRNAs (miRNAs) and their messenger RNA (mRNA) targets to identify key regulators of drought tolerance. Using a bioinformatics approach on public RNA-sequencing data from drought-stressed cowpea, differentially expressed miRNAs and mRNAs were identified. These were then used to construct an integrated miRNA-mRNA regulatory network, and centrality analysis was applied to pinpoint the most influential "hub" regulators. The analysis revealed a core set of hub miRNAs, including the conserved miR396, miR172, and miR156 families, that orchestrate the drought response. These hubs regulate critical target genes involved in stress hormone synthesis (ACC oxidase), protein stability (Heat Shock Protein 70), and antioxidant defense (Sulfate Transporter, Cysteine proteinase). Additionally, this study resulted in the identification of 31 novel miRNAs, which, however, require laboratory validation. This discovery highlights a coordinated survival strategy where a few master-switch miRNAs control a wide array of protective functions. This research provides a foundational "molecular blueprint" of cowpea's drought response, identifying high-priority candidate genes for developing climate-resilient varieties. By elucidating these regulatory hubs, this work offers a clear path for targeted breeding and biotechnological interventions to safeguard this essential crop